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DIAMINO EXPERIMENT IN

OSIRIS MTR FOR MINOR

ACTINIDES RECYCLING

PROGRAM

NOVEMBER 18 2014

IGORR 2014 | Bariloche| Stéphane BENDOTTI, Cédric NEYROUD, Syriac BEJAOUI

19 NOVEMBRE 2014 | PAGE 1 CEA | 10 AVRIL 2012

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OUTLINES

Introduction Diamino device description Irradiation environment Device design, neutronic studies Device design, thermal studies First irradiation cycles Other cycles Conclusion

19 NOVEMBRE 2014 | PAGE 2 CEA | November 18 2014

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INTRODUCTION


Americium recycling in SFR

Transmutation of minor actinides in radial blanket of GEN IV sodium-cooled reactors

Heterogeneous Am-recycling on UO2 matrix for :

But: Low irradiation temperature (from 500 °C to 1500 °C), hight helium production, risk of swelling,

no feedback.

INTRODUCTION

Diamino experiment goal

Behaviour of Americium 241 actinide element only

Two irradiation temperatures (600 °C and 800 °C)

Two burn-up rates

Two microstructures analysis (one with standard density and one with open porosity)

With any batches of post irradiation examination


IRRADIATION ENVIRONMENT

Irradiation outside the shielded box of the reactor core, to limit :

The acceleration factor of the burn-up on matrix behaviour,

the thermal gradient in the UO2 discs,

and the overheating of the discs.

As power heating and neutronic flux decrease outside the reactor box.

The furnace is inserted in a water box that channels a cooling water flow.




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Shielded

glove box

DIAMINO DEVICE DESCRIPTION


Top of the PHAETON furnace Heater connectors

Thermocouples connectors

Gaz gap connection

Furnace without external tube and copper

layer 6 independent heaters in the last bottom 600 mm of the furnace, placed on the internal tube

Hydrodynamic nozzle

Total height (not shown) : 4500 mm



Connector box

Nut for furnace

connection Sealed passage

Bioshield

Fission products filters


Loading sample holder UO2 discs placed in TZM cups,

TZM cups sealed in inconel 600 mini-pins

Mini-pins inserted in 2 inconel 600 half shells

Thermocouples inserted in shell grooves

Irradiated zone : ~600 mm height

Total height : 4500 mm




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DEVICE DESIGN, NEUTRONIC STUDIES

Neutronic calculations allow to determine: Thermal input parameters : gamma heating & initial fissile power (Tripoli-4) and it’s evolution (APOLLO2 2D)

Dosimetric parameters : neutronic flux spectrum and distribution inside the device

Helium rate production, burn-up and period of irradiation, in each fuel disc

Radioprotection input parameters : radio-isotopes inventory evolution (Darwin/Pepin2)


The decrease of the power density during reactor shutdown is real, but linear decrease is due to the lack of data.

Gamma heating evaluations are ~ 25 % upper than measured one.

But transport calculations are not yet validated, a correction of 30% is now applied because delayed neutrons are not computed.

Therefore we prefer to take into account measured values for thermal model.

DEVICE DESIGN, THERMAL STUDIES

The thermal studies allow to : Determine the correction to apply between the sample holder thermocouples to obtain the mean

temperature of the discs in front,

To avoid overheating of the tube of the furnace, the sample holder and all the structures,

To evaluate the regulation capacity of the furnace and the gas mix process,

To optimize the position of the thermocouples to avoid strong gradient fields,

To controle the thermal gradient inside the discs,

19 NOVEMBRE 2014 | PAGE 10 CEA | november 18 2014 LS-Dyna mesh for pre-irradiation studies


Thermal studies using LS-DYNA,

have been conducted for preliminary

calculations for sensibility at :

Furnace power, time of irradiation,

furnace gases,

to fix the geometrie of gas gaps,

sample holder and mini-pins

materials.

On graph, red pattern peaks show

temperature gradient in the fuel discs.

It increase between the begining (top

graph) and the end (bottom graph) of

irradiation with the fission power.

Pink rectangles give the position and

their relative electrical power.


Thermal mock-up Same position in irradiation, identical device with mini-pins, but without fuel, two more TC points

inside mini-pins TZM to caracterized heat leaks on loading end.

LICOS numeric model:

The thermal mock-up has allowed to specify gamma heating in the device and it’s radial

distribution. By adjusting thermal levels and gradients, calculated and measured between furnace,

sample holder and mini-pins TZM.

We have to increase a little the expected value to fit well the measure temperature distribution

observe in the device.

But for this cycle of irradiation DIAMINO was in front of used reactor fuels, and in case low burn-

up loading here, we have to expect significant increment in gamma heating.



COMPARISON

MEASURED/CALCULATED VALUES

Calculation/measurement comparison for 5 major configurations


Thermal chart for helium gas gaps and heaters turn-

off.

Other cases simulated: Helium gas and furnace at 24%

Helium gas and furnace at 45 %

Helium/neon 50% mix gas and furnace turn-off

Helium/neon 50% mix gas and furnace at 10%

FIRST DIAMINO CYCLE IRRADIATION

But with the increase of the fission power, it would be impossible to limit the

temperature at 600°C and 800 °C within the discs, in same conditions, from the end of

this first cycle.

It appears that we cannot transposed the gamma heating measured in the graphite on

stainless steel in the same way as we do in the core box of the reactor.

The water box was changed for the next irradiations, to back the device off the core.

All thermal and neutronic calculations were updated to take into account, new burn-up

evolution and new gamma heating.

At the beginning of the third cycle, the temperature was as shown on the graph

hereafter.


OTHER CYCLES

Neon gas as been abandoned since the second cycle and the common heater in front of the

mini-pins n°4 and n°5 was turned-off because of the slight overheating of the n°5.

5 cycles for 91 EFPD under irradiation have been currently achieved.


CONCLUSION

After 5 cycles of irradiation in OSIRIS MTR:

It appears that the global thermal behaviour of the device is consistent

with the expected one, with two distinct levels of temperature.

However we have observed a significant overheating of the samples,

due to the underestimation of the gamma heating.

The temperature regulation may be revised upwards without impact on

the objectives of the experiment. Near 880 °C at the end of the

irradiation for the upper loading and near 640 °C lower loading.

Post Irradiation Examination will be drives on fuel discs to caracterized

the behaviour.


Direction

Département

Service

Commissariat à l’énergie atomique et aux énergies alternatives

Centre de Saclay | 91191 Gif-sur-Yvette Cedex

T. +33 (0)1 XX XX XX XX | F. +33 (0)1 XX XX XX XX

Etablissement public à caractère industriel et commercial | RCS Paris B 775 685 019 19 NOVEMBRE 2014

| PAGE 17

CEA | 10 AVRIL 2012

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